A polycarbonate copolymer has been used as a material for moldings in various industrial fields because of its excellent mechanical characteristics, thermal characteristics and electrical characteristics. Recently, the polycarbonate copolymer has often been used in a field of a functional product requiring optical characteristics of the polycarbonate copolymer as well as the above characteristics. In accordance with such an expansion in application, the polycarbonate copolymer has been demanded to have a variety of performance. Not only a typically used polycarbonate copolymer but also polycarbonate copolymers having various chemical structures have been proposed.
The functional product is exemplified by an electrophotographic photoreceptor in which the polycarbonate copolymers are used as a binder resin for functional materials such as a charge generating material and a charge transporting material.
The electrophotographic photoreceptor has been demanded to have a predetermined sensitivity, electrical characteristics and optical characteristics in accordance with electrophotography process to be applied. A surface of a photosensitive layer of the electrophotographic photoreceptor is repeatedly subjected to operations such as corona electrification, toner development, transfer onto paper, cleaning and the like. Accordingly, electrical and mechanical external-forces are applied on the surface of the photosensitive layer every time such operations are performed. Consequently, the photosensitive layer provided on the surface of the electrophotographic photoreceptor is required to have durability against these external forces in order to maintain electrophotography image quality for a long period of time. Moreover, since the electrophotographic photoreceptor is typically manufactured by dissolving a functional material and a binder resin in an organic solvent and film-casting the obtained solvent on a conductive substrate and the like, the electrophotographic photoreceptor is required to have solubility in the organic solvent and stability of the obtained solvent.
Polycarbonate copolymers disclosed in Patent Literatures 1 to 3 have been known as polycarbonate copolymers satisfying the above properties.
Patent Literature 1 and Patent Literature 2 disclose a polycarbonate copolymer containing 1,1-bis(4-hydroxyphenyl) cyclohexane (bisphenol Z) and biphenol. Patent Literature 3 discloses a PC copolymer containing: 4,4′-dihydroxy-3,3′-dimethylbiphenyl; and 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane or 2,2-bis(3-methyl-4-hydroxyphenyl)propane (bisphenol C).
As a high quality image has been increasingly used in recent years, an AC/DC superimposing electrification method in which an AC voltage is superimposed on a DC voltage is used as a method of electrifying a surface of a photosensitive layer of the electrophotographic photoreceptor. According to the AC/DC superimposing electrification method, stability of the electrophotographic photoreceptor is improved, whereas an electrical discharge amount of a surface of the electrophotographic photoreceptor is drastically increased since the AC voltage is superimposed. For this reason, a resin is deteriorated to increase wear volume of the electrophotographic photoreceptor. Accordingly, the electrophotographic photoreceptor has been required to have electrical strength in addition to the mechanical strength.